Various types of conventional electrical and electromechanical components require packaging in a clean hermetically sealed volume to function properly. For example, Radio frequency microelectromechanical (RF MEMS) technology provides moving sub-millimeter-sized components with RF functionality. Examples of RF MEMS components include resonators, oscillators, switches, switched capacitors, varactors, etc. As mentioned above, the functionality of components from RF MEMS and other technologies depends on the ability to provide the components in hermitically sealed environments.
In some conventional approaches, often referred to as wafer-level packaging, the components are provided within respective cavities formed in a surface of a silicon wafer. A set of seal ring metallization stacks (also referred to herein simply as seal rings) is provided on the wafer surface (e.g., using a metal lift-off process) in surrounding relationship to the respective cavities. Another wafer is provided with a similar set of seal ring metallization stacks on its surface. The pair of wafers is positioned in opposing relationship with their respective sets of seal rings aligned such that each seal ring on one wafer is in opposed relationship to a corresponding seal ring on the other wafer. This is illustrated in FIG. 1, which shows an opposed pair of seal rings 13 and 14 on an aligned pair of wafers 10 and 11, with the seal ring 14 surrounding a cavity 12 in wafer 11 where the component (also referred to herein as the “device”) is provided.
The opposed pairs of seal rings are then moved forcibly into contact with one another, as shown in FIG. 2, and bonded together using a suitable bonding technique, such as eutectic bonding, thereby packaging the components between the two wafers 10 and 11, with each component hermetically sealed within its cavity 12 by the associated pair of aligned and bonded seal rings 13 and 14. In some instances, the resulting bonded wafer assembly is then sawed to singulate the packaged components for individual deployment. In other instances, the entire bonded wafer assembly is deployed in a larger assembly. Various conventional connection arrangements (not explicitly shown in FIG. 2) are available to permit electrical access to the packaged components externally of their sealed cavities. The configuration of the connection arrangement depends on the mode, of deployment of the packaged component.
Conventional seal ring bonding processes forcibly compress the opposed seal ring pairs against one another. This may cause the seal ring metallizations to deform beyond what is necessary for bonding, with various attendant problems.
It is therefore desirable to provide for controlling compression during seal ring bonding.